Complex manufacturing processes such as, for example, chemical manufacturing processes, typically involve many steps, each of which utilizes different inputs and different processing equipment. These process steps may occur in series or in parallel or both, and may or may not be time dependent upon the completion of other steps in the process. It is well known to utilize process control computers to collect information relating to a single step or number of steps in a process and display that information in a format recognizable by a human operator. It is also well known to utilize appropriately programmed computers to automate selected steps of a manufacturing process, thereby reducing the need for constant human interaction with each of the process components during processing. These process control computers may virtually automate one or more steps in a process, while providing information in human readable format to allow for human monitoring with human control limited to fine tuning of the process or crisis intervention.
For simpler manufacturing processes, the complete process may be automated through the use of a process control computer. However, larger and/or more complex manufacturing processes are effected through the of a plurality of process control computers, each controlling a portion of the complete manufacturing process.
Process Terminology
The effective control and supervision of a complex manufacturing process involves assimilation of information from three domains or realms. As used herein, the terms "datalogical," "infological," and "physical" are each used to denote different realms or domains associated with process control. The physical realm includes the physical components of a process, such as, for example, a pump, or its associated inputs and outputs. The datalogical realm includes computer representations of data, such as, variables, flags, etc., which are defined and utilized by the computer. In contrast, the infological realm is human-interface oriented data which may represent, or is derived from, the physical realm or the datalogical realm. The change in physical quality may have datalogical as well as infological implications. For example, a switch changing from closed to open (an event in the physical realm) may change the datalogical quality of a digital variable (e.g., from TRUE to FALSE or OFF to ON) corresponding to the computer representation of the state of the switch. At the same time, the change in state of the switch may mean that, for example, a pump is on. In the infological realm this same event may be represented as a flashing or color-coded icon representing the pump, or by the words "Pump On," or "Flow Equals 100 CFM" appearing on a display. As will be appreciated by those skilled in the art, the control of a manufacturing process involves each of the physical, datalogical and infological realms. Through the efficient mapping of information within these realms a human operator can more effectively supervise and control the manufacturing process.
To more efficiently control and supervise increasingly complex manufacturing processes, the physical, datalogical, and informational attributes associated with these processes have been subdivided into a plurality of SEQUENCES. A SEQUENCE is an infological construct (or object) which has associated with it a set of physical components which are utilized in the process, such as a boiler and the input valves and output valves associated with the boiler. The domain of a SEQUENCE also may include selected inputs (digital or analog) from the physical components of the manufacturing process, as well as selected variables, such as those defined and utilized in the process control computers. Another attribute associated with a SEQUENCE includes the set of steps involving the physical components associated with that SEQUENCE, which steps are defined in a manufacturing process control program implemented by a process control computer. It should be noted that, despite its name, the steps in a SEQUENCE are not necessarily implemented sequentially. That is, a SEQUENCE may change from one step (or state) to any other step in the SEQUENCE, not necessarily "the next" step on the list. Other common data attributes of a SEQUENCE are alarms, recipes, and minimum/maximum values for selected variables.
Thus, while a SEQUENCE in its narrowest sense may be associated with a set of steps or physical components associated with a manufacturing process, a SEQUENCE may be broadly considered to define a domain associated with a manufacturing process that includes physical components associated with the process, data associated with the process, and other infological elements derived from, or representative of, combinations of physical elements and/or data associated with the process. As used hereinafter, SEQUENCE is intended in this broader definition which encompasses attributes from each of the physical, datalogical, and infological realms.
It should be noted that certain elements such as, for example, variables, may be associated with more than one SEQUENCE. That is, an attribute of a SEQUENCE is not necessarily uniquely associated with that SEQUENCE, but may also be an attribute of a different SEQUENCE.
As used herein, process "primitives" are the operator station symbols representing (1) basic points of control interaction between the PCC and the physical process and (2) other variables in the PCC. Primitives include, for example, symbols identified with PCC variables, such as component quantities, process parameters, digital and analog inputs and outputs, and PCC-defined variables and alarms.
"Recipes" are collections of data referenced within a SEQUENCE which enable variables coded in a genus context to represent a particular species of product, raw material, and/or manufacturing process. In a chemical manufacturing process cycle, recipes typically include a list of related component quantities and process parameters which will remain fixed during that cycle. As an example of the use of recipes, consider a reactor system programmed generically to use a RECIPE.sub.-- WEIGHT of component A, to heat to a RECIPE.sub.-- TEMPERATURE, and to store the product in the RECIPE.sub.-- PRODUCT.sub.-- TANK. In a manufacturing cycle to produce chemical #1, the recipe values will be:
RECIPE.sub.-- WEIGHT=500 lbs PA1 RECIPE.sub.-- TEMPERATURE=120 deg C. PA1 RECIPE.sub.-- PRODUCT TANK=4 PA1 RECIPE.sub.-- WEIGHT=800 lbs PA1 RECIPE.sub.-- TEMPERATURE=130 deg C. PA1 RECIPE.sub.-- PRODUCT.sub.-- TANK=1 PA1 They appear in a number of application windows. PA1 They behave in a similar manner whenever they are subjected to an interrupting impulse. The reason for this is that each common element is preferably related to a specific common element class having defined associated data types and manipulation response attributes for all individual manifestations of that common element associated with that particular class. As an example, in the current embodiment of the invention, all common element process primitives represented on the operator station as analog inputs in the PCC will, when represented on the operator station by the process primitive designed for the purpose of depicting analog inputs, always display the same predictable dialog box to the human operator when any given analog input process primitive is "clicked upon" by the human operator. PA1 They are all subject to the same kind of manipulation either by an operator or by the operator station system software. PA1 Process Inputs--graphical objects which are associated with PCC data values (including analog inputs and/or digital inputs in the PCC wherein the analog and/or digital inputs are individually associated with field instrumentation used to measure manufacturing apparatus attributes such as temperature, pressure, flow, or valve position; PA1 Process Outputs--graphical objects which are associated with PCC data values (including analog and/or digital outputs in the PCC wherein the analog outputs and digital outputs are individually associated with field instrumentation which directly affects and modifies the manufacturing apparatus in a dynamic sense, since the outputs are delivered to field devices (such as pumps, valves, agitators and mixing devices, such as impellers, which are components in the manufacturing apparatus). PA1 Process Variables--graphical objects which are associated with PCC data values which are not directly associated with field instrumentation but are either periodically changed by either the process control computer or by a human being. In the case where the PCC recomputes the value of the process variable, the frequency of value change will be very high; in the case where the human being changes the process variable, the frequency of change should be very low. Process Variables are differentiated here in terms of being different than Process Inputs and Process Outputs in that they are not PCC data items which are consistently associated with field instrumentation. In the case of the human changeable Process Variable, the term "Process Constant" is used to further distinguish the expected change frequency. PA1 Alarm Variables--graphical objects which are associated with process control computer data values which function to alert humans and set status indicators in the process control computer when specific events occur which require either human attention or an altered process control methodology. Usually, these events are considered to be interruptions in the ideal progression of the manufacturing cycle. PA1 the SECTIONS Overview Window; PA1 the SEQUENCES Overview Window; PA1 the Plant Overview Flowsheet Window; and PA1 the Flowsheet-Dependent Trend Window. PA1 the Main Menu; and PA1 the Unacknowledged Alarm Overview Window. PA1 Operations to modify variables to which change of value is permitted through the process control communications system where the human operator is not forced to proceed through a security-related process when the individual value change is being attempted will be referenced as "Manual Data Writes" since they represent data write operations to the PCC database which are manually initiated by a human being from the operator station; PA1 Operations to modify variables to which change of value is permitted through the process control communications system only when the human operator has been forced to proceed through a security-related process at the time when the individual value change is being attempted will be referenced as "Bypass Manual Data Writes" since they represent data write operations to the PCC database which are manually initiated by a human being from the operator station wherein the incoming message to the process control communications system must bypass the normal security filter applied by the process control communications system to incoming messages directed to modification of variables in the process control computer. The ability for an individual message to bypass the filter is derived from a change in the message content and data structure as a result of the human operator proceeding through the security-related process at the time that the change of value message is being formulated in the operator station. In the preferred embodiment, a Bypass Manual Data Write is implemented in three steps. First, the operator opens a Dialog Box for the selected variable and enters its new value. Second, the operator opens a security Dialog Box by clicking on the PCC indicator for the PCC with which the selected variable is associated and inputs the appropriate security code. Third, the operator must then click on the send button in the change Dialog Box within a pre-determined time period. If the operator does not complete this third step within the pre-determined time period, the security code is rendered invalid for this operation and must be re-entered. The time period related to the security code is restarted after each successful Bypass Manual Data Write, thereby enabling the operator to perform a series of associated Bypass Manual Data Writes for one security code entry. PA1 Real-time monitoring of selected alarms, grouped in a logical order in a grid on a graphic sheet (in the Alarm Grid Flowsheet Window); PA1 Real-time monitoring of one or more alternative sets of active alarms in a manner similar to that of the Active Alarms Window discussed above, but filtered and sorted in a different context; PA1 Real-time monitoring of items under manual control (in the "Elements-In-Manual Window"); PA1 Real-time monitoring of categories of system event messages received from one or more PCCs (in the Real-Time Event Capture Window). As used herein, system event messages are unsolicited data or status messages received by the operator station from other components of the manufacturing process control system, such as a PCC or a process control communication system (both as hereinafter defined); and PA1 Reviewing the operator station's event log of PCC system messages over a given time period, based on specified filtering criteria (in the Event Browser Window). PA1 A pie-chart that indicates the actual value; and PA1 A rotating line segment that indicates the trailing average of the CSF value.
In the subsequent manufacturing cycle to produce chemical #2, which will use the same steps as were used by chemical #1, the recipe values will be:
The PCC code for the equipment is written to add component A until the (generic variable) RECIPE.sub.-- WEIGHT is achieved, to then heat component A to the RECIPE TEMPERATURE, and to open a valve to storage based upon the RECIPE.sub.-- PRODUCT.sub.-- TANK. As is apparent to one skilled in this art, the "Recipe" feature in the system enables PCC code to be written for a family of chemicals and then used to make different species of the family (or genus) without the need for reprogramming or substantial manual alteration of PCC variables as the system moves from species to species in its subsequent manufacturing cycles. The only input necessary for the species variables to be included is that the SEQUENCE be instructed to make either chemical #1 or chemical #2 as the recipe for that manufacturing cycle--the PCC will then select the appropriate set of recipe values to be used whenever a recipe generic variable is referenced in the control program.
"Alarms" are variables associated with elements in the process (which have their own process primitives) utilized to signal abnormal or unstable situations. Various categories of alarms may be implemented to indicate, for example, different levels of significance to the process. In many of the chemical processes controlled by PCCs at The Dow Chemical Company, six alarm categories are utilized. These categories are (in descending order of degree of severity) Shutdown Alarms, Emergency Alarms, Warning Alarms, Alert Alarms, Min/Max Alarms, and Request alarms.
When an alarm variable has changed to the "on" or "active" state, the PCC regards it as an unacknowledged alarm, until an operator has taken action to acknowledge the particular alarm. An acknowledgement action typically includes either activating a hardware switch associated with the alarm variable or setting a software switch associated with the variable through a control interface such as the operator station of the present invention.
As with alarms, a "manual" variable in the PCC has an associated state (on/off or manual/automatic) that is depicted by a corresponding state of a process primitive associated with the variable in the PCC. As used herein, when a process variable is in "manual," the value of the associated process primitive (whether it be an input or output) needs to indicate if the variable has been manually input or overridden by the operator. This manual override of the associated primitive, which is otherwise either automatically created by the PCC system or detected by the PCC from the field, may be accomplished by a hardware override (for example by flipping a switch or setting a thumb wheel), or by changing the value of the associated process primitive through the operator station via the "Change" command or by enabling a "Manual Data Write" as hereafter described. The former manual override may be referred to as a "hard manual," while the latter manual override, effected through the operator station, may be referred to as a "soft manual."
Thus, the increasing scope and complexity of manufacturing processes, and the process control computers associated with those processes, creates a need for an efficient man/machine interface which effectively manages and utilizes physical, datalogical, and infological attributes associated with the manufacturing process and its associated process control computer(s) to convey process information to a human operator/supervisor in real-time. These interfaces, hereinafter referred to as "operator stations" must provide the operator/supervisor with the ability to supervise increasingly larger and more complex operations.
As used herein, real-time processing is generically defined as a method of processing in which an event causes a given reaction within an actual time limit and wherein computer actions are specifically controlled within the context of and by external conditions and actual times. As an associated clarification in the realm of process control, real-time processing relates to the performance of associated process control logical, decision, and quantitative operations intrinsic to a process control decision program functioning as part of a controlled apparatus and its associated process wherein the process control decision program is periodically executed with fairly high frequency usually having a period of between 20 ms and 2 sec, although other time periods could be also utilized and some operations might be performed on an integer multiple of the primary process control decision program execution period for purposes related to either tuning, sensitivity, or efficient resource utilization.
Furthermore, existing process control computers typically provide information in human readable format to allow an operator to supervise and control that portion of the manufacturing process. However, when a conventional operator station receives information from, and transmits control signals to, more than one process control computer, the increased volume of process data presents an increasingly serious sensory overload upon the human operator responsible for supervision and control of the system.
A method is needed to present the data in an organized context to minimize the amount of data required by the operator in order to efficiently supervise the ongoing process. A system is needed to present the expanded amount of data in an organized context which minimizes the sensory overload for the human operator while enabling the human operator to effectively manage the more complex process control situation; the present invention fulfills these needs.
One object of the present invention is to provide an operator station which provides selected process data from at least two dedicated process control computers for simultaneous monitoring and control of the portions of the manufacturing process governed by each of the dedicated process control computers.
Another object of the present invention is to provide an operator station which provides to a human operator information for, and allows supervision and control of, a plurality of SEQUENCES of one or more manufacturing processes.
Another object of the present invention is to provide an operator station for a manufacturing process control system including a fixed format display providing selected information relating to each of one or more pre-defined SECTIONS (as hereafter defined) monitored by the system, selected information relating to a selected one or more of the SEQUENCES monitored by the system, and one or more additional displays which may be varied in the format of presentation of selected process data relating to the manufacturing processes supervised and controlled through the operator station.
Another object of the present invention is to provide an operator station for a manufacturing process control system including infological objects which graphically and succinctly communicate to the operator the current status of a SECTION, where the infological object is a composite of preselected parameters associated with the SECTION.
Another object of the present invention is to provide an operator station for a manufacturing process control system including infological objects which graphically and succinctly communicate to the operator the current status of a SEQUENCE, where the infological object is a composite of preselected parameters associated with the SEQUENCE.
Another object of the present invention is to provide an operator station for a manufacturing process control system including infological objects which graphically and succinctly communicate to the operator the current status of a predefined collection of PCC variables represented by process primitives, where the infological object is a composite of preselected parameters associated with a physical field device or controller.
Another object of the present invention is to provide an operator station for a manufacturing process control system including a display having a fixed format including a first window with standard graphic indicia representing the status of preselected parameters for the SECTIONS of the processes, a second window with standard graphic indicia representing the current status of one or more selected SEQUENCES in the process, a third window including information in the form of a graphic sheet, such as a flowsheet, including standardized graphic indicia identifying the significant steps or components in a selected SEQUENCE of the process, and selected additional process data relating to those steps and components.
Another object of the present invention is to provide an operator station for a manufacturing process control system including a display having a fixed format including a first window with standard graphic indicia representing the status of preselected parameters for the SECTIONS of the processes, a second window with standard graphic indicia representing the current status of one or more selected SEQUENCES in the process, a third window including information in the form of a flowsheet including standardized graphic indicia identifying the significant steps or components in a selected SECTION of the process, and selected additional process data relating to those steps and components.
It is another object of the present invention to provide an operator station which presents process data relating to a plurality of manufacturing processes, thereby enabling human supervision of the plurality of manufacturing processes from a single physical location.